fix: fetch item_tax_template values if fields with fetch_from exisit

erpnext/controllers/accounts_controller.py

@@ -625,6 +625,7 @@ class AccountsController(TransactionBase):
 
 					args["doctype"] = self.doctype
 					args["name"] = self.name
+					args["child_doctype"] = item.doctype
 					args["child_docname"] = item.name
 					args["ignore_pricing_rule"] = (
 						self.ignore_pricing_rule if hasattr(self, "ignore_pricing_rule") else 0